The project is designed to develop animal model systems to meet the requirements of a broad spectrum of research programs to include immunology, infectious diseases, parasitology, behavior, neurological disorders, metabolic diseases, and cardiovascular disorders in small animals utilizing the closed breeding groups maintained by the NIH Animal Genetics Resources. The project is collaborative in nature in that all of the breeding programs are carried out internally and the evaluation of the model is performed by the research community. During the year, evaluations were completed on two models, one in the mouse and the other in the rat. A colony of immunocompromised mice was established on the N:NIH outbred background by combining three genes, nude (nu), beige (nu), and X-linked immune defect (xid), all of which affect various components of the immune system. The results of an initial test indicate that mice carrying these genes is a superior model for heterotransplantation of human tumor material to ordinary nude mice which have been previously used for this purpose. In the rat, the SHR/N-cp (corpulent) congenic strain promises to be a useful model for insulin independent diabetes as well as the role that brown fat plays in regulating body temperature. Other mouse and rat models are currently under evaluation.